Bioethanol production from various lignocellulosic feedstocks by a novel "fractional hydrolysis" technique with different inorganic acids and co-culture fermentation. (15th January 2019)

• Record Type: Journal Article
• Authors: Mishra, Archana; Ghosh, Sanjoy
• Is Part Of: Fuel. Volume 236(2019)
• Page Start: 544
• Page End: 553
• Publication Date: 2019-01-15
• Subjects: Bioethanol -- Inorganic acids -- Saccharification -- Fractional hydrolysis -- Co-culture fermentation; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2018.09.024
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Four different inorganic acids were used in novel fractional hydrolysis technique. Three different lignocellulosic feedstocks were explored for the process. Maximum 84.88% of TRS was recovered from the kans grass biomass using H2 SO4 . A unique co-culture approach using Z. mobilis and C. shehatae was developed. Average ethanol yield (YP/S ) was 0.44 using the kans grass hydrolysate media. Abstract: Second generation (2G) ethanol production is facing major research challenges primarily because of an absence of suitable technology for the extraction of maximum fermentable sugars from complex lignocellulosic structure as well as unavailability of suitable fermentation technique and single microorganism to convert these sugars (pentose and hexose) efficiently into ethanol. Present study is focused on the exploration of various lignocellulosic feedstocks using different inorganic acids for the recovery of maximum amount of fermentable sugars as separate fractions, direct from the biomass by a novel process called "fractional hydrolysis" with minimum toxics generation. Different physical and chemical parameters were optimised for the process previously. Four different inorganic acids (HCl, H3 PO4, HNO3, and H2 SO4 ) up to 30% concentration (v/v) were used in 7- and 8-stage fractional hydrolysis processes to treat dry biomass in a fractional hydrolysis column. Using kans grass biomass, H2 SO4 resulted in maximum extraction of pentose and hexose sugars separately with negligible toxics. Furthermore, the technique was explored using three different wide and easily available lignocellulosic feedstocks, resulting in saccharification (%): Kans grass 84.88; Sugarcane bagasse 82.55; Wheat straw: 81.66. Hydrolysate fractions without any detoxification were taken into a co-culture system containing Zymomonas mobilis (for glucose fermentation) and Candida shehatae (for xylose fermentation) at bioreactor level. 93.28% of the sugar present in xylose-rich fraction (initial total reducing sugar: 59.74 g/L) and 95.44% of glucose-rich fraction (initial total reducing sugar: 100.25 g/L) were utilised to produce 67.28 g/L ethanol from the kans grass biomass hydrolysate; thereby achieving 82.45% of the maximum theoretical ethanol production.